A. Technical Field
The present invention relates to: a catalyst used for production of acrylic acid; and a process for production of acrylic acid using this catalyst. Specifically, the present invention relates to: a catalyst for production of acrylic acid, wherein the catalyst is excellent in such as activity, selectivity, and physical strength; and a process for production of acrylic acid, wherein the process comprises the step of carrying out catalytic gas phase oxidation of acrolein in the presence of molecular oxygen in the presence of the above catalyst, thereby producing the acrylic acid.
B. Background Art
As a catalyst for efficiently producing acrylic acid by catalytic gas phase oxidation of acrolein (catalyst for production of acrylic acid), there is often used a catalyst which is obtained by a process including the steps of: for example, adding a liquid binder to a catalytic component powder obtained from a mixed liquid of starting materials including molybdenum and vanadium as essential components; and then molding the resultant mixture; and then calcining the resultant molding. As to processes for producing this catalyst, various proposals have been made.
Examples of these production processes include: (1) a process including the steps of evaporating a mixed liquid of starting materials to dryness, and then adding polyvinyl alcohol, a water-absorbent resin, and water to the resultant dried material, and then kneading the resultant mixture, and then extrusion-molding the kneaded mixture (for example, refer to JP-A-096183/1993); (2) a process including the steps of spraywise drying a mixed liquid of starting materials, and then calcining the resultant dried material at 400° C., and then supporting the resultant calcined structure onto a carrier using water as a binder with such as a rotating drum type supporting apparatus (for example, refer to JP-A-279030/1994); (3) a process including the steps of drying a mixed liquid of starting materials by any method of evaporation to dryness, spray drying, drum drying, and gas flow drying, and then adding propyl alcohol and water to the resultant dried material to mix them together, and then extrusion-molding the resultant mixture (for example, refer to JP-A-010621/1996); (4) a process including the steps of spraywise drying a mixed liquid of starting materials and then calcining the resultant dried material at 400° C., and then supporting the resultant calcined structure onto a carrier using a liquid binder including water and an organic compound having a boiling point or sublimation temperature of higher than 100° C. under normal pressure (for example, refer to JP-A-252464/1996); and (5) a process including the steps of drying a mixed liquid of starting materials, and then calcining the resultant dried material in the range of 250 to 500° C., and then supporting the resultant calcined structure onto a carrier using such as an aqueous glycerol solution as a binder with a tumbling granulator (for example, refer to JP-A-299797/1996 and JP-A-079408/2001).
The above liquid binder is used for the purpose of such as 1) to 4) below. 1) Providing the catalytic component powder with moderate viscosity and flowability, thereby reducing the friction force between a molding machine and the catalytic component powder and/or between particles of the catalytic component powder during the molding; 2) intending to enhance the moldability such as the molding speed, the uniformity of the molded shape, the yield, and the workability (handling ability); 3) intending to enhance the binding force between particles of the catalytic component powder (this leads also to the enhancement of the physical strength of the catalyst) and, in the case of obtaining the supported catalyst, intending to promote and strengthen the binding and fixation between the carrier and the catalytic component powder; or 4) forming pores in the catalyst by utilizing the removal of the binder from the molding due to heating (e.g. calcining) after the molding.
However, all the catalysts for production of acrylic acid, which are obtained by the above prior processes, are still insufficient as to: the catalytic performances such as catalytic activity; and the physical strength of the catalysts themselves.